1. Field of the Inventions
The present inventions relate to torque dampers for transmitting torque input to a cover of a torque converter (hereinafter referred to as “a torque converter cover” or simply as “cover”) to a turbine via a clutch piston and connecting members.
2. Description of the Related Art
A torque converter (fluid coupling) equipped on an AT (automatic transmission) vehicle usually comprises a torque converter cover in which liquid (working fluid) is contained in a substantially liquid-tight condition. A pump is typically rotated together with the torque converter cover, a turbine is arranged oppositely to the pump, a stator is connected to a one way clutch and the rotation of pump can be transmitted to the turbine via the liquid and can increase the transmitted torque. Accordingly the driving torque of engine can be boosted via the liquid and transmitted to a transmission and driving wheels of a vehicle.
A torque damper is sometimes included within the torque converter cover and is intended to reduce torque transmitting loss by directly connecting the torque converter cover and the turbine at an appropriate timing as compared with the torque transmission via liquid. This type of torque converter is often referred to as a “lockup torque converter”. That is, the torque damper has a clutch piston adapted to be connected to the turbine and can be moved between a connected position in which the clutch piston is abutted against an inner circumferential wall of the torque converter cover and a non-connected position in which the clutch piston and the torque converter cover are separated and thus the torque converter cover and the turbine can be directly connected via the clutch piston at the connected position.
Damper springs are arranged on the clutch piston for absorbing torque variations from an engine in the connected condition of the torque damper. A plurality of the damper springs are arranged along the outer circumferential edge of the clutch piston in a circular arc arrangement and can be displaced (expanding and contracting) to absorb the torque variation transmitted from an engine when the clutch piston is in the connected position. For example, Japanese Laid-Open Patent Publication No. 126298/1997, discloses such a torque converter.
In the prior art disclosed in the Japanese Patent Document No. 126298/1997, guide sheets having wear resistance are arranged between the circumference of the clutch piston and the damper springs to reduce wear of the springs during their expansion and contraction. A portion of each guide sheet is anchored to the clutch piston to prevent the guide sheet from being moved circumferentially. More particularly, the guide sheet is anchored to the clutch piston by inserting a portion of the guide sheet folded radially outward of the clutch piston into a notch formed in a wall portion axially standing at the circumference of the clutch piston.